<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
  <style>
    #d1{
      width: 100px;height: 100px;
      border: 10px ridge red;
      /*设置圆角，值越大越圆，当值超过宽高的一半时，边框为一个圆*/
      border-radius: 10px;
    }
    #d2{
      width: 200px;height: 200px;
      border: 2px solid blue;
      /*给元素添加内边距
      默认情况下会影响元素的宽高*/
      padding-left: 100px;
      padding-top: 100px;
      /*设置元素内边距不影响元素宽高*/
      box-sizing: border-box;
    }
  </style>
</head>
<body>
<div id="d2">内边距测试</div>
<div id="d1">边框测试</div>

</body>
</html>